1. Field of the Invention
The invention concerns adhesive strips applied to the skin for removing keratotic plugs from pores and concurrent delivery of skin benefit agents.
2. The Related Art
A variety of vehicles exist for delivery of actives to the skin. These vehicles may be lotions, creams, pads, sprays and even masks. Some are leave-on systems while others are intended as short-lived wash-off products. Those who practice cosmetic arts know the critical role that vehicles perform in delivering actives effectively to skin.
Delivery is not the only concern. Some types of actives are degraded by the vehicle. For instance, ascorbic acid, also known by its common name of Vitamin C, is a very unstable substance. Although readily soluble in water, rapid oxidation occurs in aqueous media. Solubility of ascorbic acid has been reported to be relatively poor in nonaqueous media, thereby preventing an anhydrous system from achieving a significant level of active concentration. Derivatives have been produced with greater stability than the parent component. See U.S. Pat. No. 5,137,723 (Yamamoto et al.) and U.S. Pat. No. 5,078,989 (Ando et al.). A two-pack approach has been developed where Vitamin C powder and other ingredients are separately packaged in different containers with mixing just prior to use. See U.S. Pat. No. 4,818,521 (Tamabuchi). Water compatible alcohols such as propylene glycol, polypropylene glycol and glycerol have been used as co-carriers alongside water to improve stability. See U.S. Pat. No. 4,983,382 (Wilmott and Znaiden).
Vitamin C is just one example of difficult to formulate cosmetic ingredients. Many other types of vitamins, herbal extracts and alpha- or beta-hydroxycarboxylic acids have one or more properties which render them sensitive to certain types of delivery vehicles.
Masks have been employed to deliver herbal extracts to the face. Among the extracts have been glycyrrhizinic acid, .alpha.-bisabolol, azulene, yarrow, coltsfoot, sage, myrrh, rosemary and others. See U.S. Pat. No. 5,614,201 and U.S. Pat. No. 5,482,710, both to Slavtcheff et al. These mask products are reported to eliminate pimples, blemishes and the redness of acne. Unfortunately delivery via masks requires the presence of significant amounts of water which may adversely react with moisture sensitive ingredients. Extended drying times are also necessary for evaporation of water from the applied mask material. Finally, masks have relatively low adhesivity. These products are insufficiently sticky to effect "rip-off" of pore plugs and accumulated dead skin cells which otherwise would be barriers or at least hindrances to the penetration of the cosmetic actives.
Within the last two years, cleansing pore strips have entered commerce in a number of countries. Products such as Kao Biore.RTM. and Pond's.RTM. Cleansing Pore Strips are sheets of an adhesive coated flexible band-aid shaped strip which when wetted have sufficient adhesivity to remove keratotic plugs from skin pores. The strips are left on the skin for approximately 15-30 minutes to allow adhesive polymer to penetrate the pores. Removal of the strip rips away the plugs as well as a layer of skin. These products do not contain any skin benefit agents. In fact, the whole concept behind the strips is removal rather than deposition.
It is an object of the present invention to provide a delivery system for vitamins, herbal extracts and hydroxycarboxylic acids which assists penetration of these actives into the human skin.
Another object of the present invention is to provide a delivery system for vitamins, herbal extracts and hydroxycarboxylic acids which does not interfere or degrade the active during storage.
These and other objects of the present invention will become more readily apparent through the following summary, detailed discussion and examples.